The effect of essential amino acid deprivation on poly(A) metabolism in Neurospora crassa

Poly(A) messenger RNa was isolated from a methionine auxotroph of Neurospora crassa grown to exponential and early stationary phases, and from mycelia deprived of the essential amino aid. The polyadenylate regions were isolated from the mRNA preparations by enzymatic digestion and affinity chromatography, and their lengths determined by electrophoresis on 10% acrylamide/90% formamide gels. There was no significant difference in the lengths of the poly(A) regions between exponential and early stationary phase cultures. However, the poly(A) regions of mRNA isolated from cells undergoing amino acid deprivation were larger and more heterogeneous than the poly(A) regions isolated from cells grown in amino acid-supplemented medium. Whole cell extracts prepared from both amino acid-supplemented and amino acid-deprived cultures were assayed for their ability to synthesize and degrade poly(A). No significant difference between the two extracts was detected in either poly(A) polymerase or poly(A)-degrading activities. It was concluded that continuing translational activity in required for the shortening of poly(A) tracts in N. crassa.     

Effect of exogenous cortisone on amino acid metabolism in rats

1. The effect of exogenous cortisone on concentration of free amino acids in serum, skeletal muscle, kidney, small intestine and liver was studied. 2. The amino acid pool in serum, skeletal muscle and small intestine decreased significantly. 3. Glutamine synthesis increased significantly in skeletal muscle. 4. Levels of branched amino acids increased in serum and small intestine. 5. Levels of alanine increased in kidney and liver.     

Effects of calcium deprivation on n-6 fatty acid metabolism in growing rats

Two separate experiments examining the effects of calcium deficiency on plasma and liver fatty acids in rats were conducted. In Experiment I, weanling male Sprague-Dawley rats were fed a calcium-deficient diet with or without the supplementation of 5 or 20 g/kg calcium for 22 days. There were no significant differences in plasma and liver fatty acid distribution between the two calcium-supplemented groups. However, calcium deficiency significantly elevated the levels of 18:3n-6 in plasma and liver cholesteryl esters and liver phospholipids, while it reduced the levels of 20:3n-6 in plasma cholesteryl esters. In Experiment II, weanling rats were fed a calcium-deficient diet supplemented with 5 g/kg calcium for 22 days. After overnight fast, animals were given by intragastric feeding a dose of 4 g/kg body wt gamma-linolenic acid concentrate (containing 92% 18:3n-6 ethyl ester), and were killed 22 hr later. The levels of 18:3n-6 were significantly higher, whereas the levels of 20:3n-6 were either not changed or lower than those in calcium-supplemented group. In both experiments, the ratios of (20:3n-6 + 20:4n-6)/18:3n-6 in plasma and liver lipids were significantly reduced in calcium-deficient rats. These results suggest that calcium may play an important and specific role in the process of elongation of 18:3n-6 to 20:3n-6.     

The effect on macromolecular synthesis of amino acid deprivation of hamster kidney cells

Since asparagine has been found to inhibit growth of some tumors and to inhibit or delay mitotic activity in other cells, we have studied the effect of asparaginase and of deprivation of some essential amino acids (Arg, Asn, Leu, Ile, Trp) on nucleic acid and protein synthesis in an asparagine-requiring strain of BHK/21 cells. We find that: (1) there is no essential difference in the pattern of synthesis following deprivation of any of the amino acids we tested; (2) that the effect of asparaginase is similar to that of amino acid deprivation; (3) that RNA synthesis is inhibited more rapidly than DNA or protein synthesis; (4) that after 10 hr of amino acid starvation, DNA synthesis is almost totally (reversibly) inhibited while RAN synthesis continues at about 30-50% and protein at about 100% of the initial value.     

Effect of pyridoxine deficiency on nucleic acid metabolism in the rat

1. The nucleic acid metabolism in the pyridoxine-deficient rat has been investigated through studies on the incorporation of radioactivity from various isotopically labelled compounds into liver and spleen DNA and RNA. 2. In pyridoxine deficiency, the incorporation of radioactivity from sodium [¹⁴C]formate was apparently increased. The magnitude of this effect on incorporation into liver RNA and DNA and spleen RNA was approximately the same. The incorporation into spleen DNA was enhanced to a much greater degree. Administration of pyridoxine 24hr. before the rats were killed reversed the changes in incorporation of radioactivity from [¹⁴C]formate. 3. In pyridoxine deficiency, the incorporation of radioactivity from dl-[3-¹⁴C]serine, [8-¹⁴C]adenine, [Me-³H]thymidine and [2-¹⁴C]deoxyuridine was decreased. The incorporation of radioactivity from l-[Me-¹⁴C]methionine was not affected. No noteworthy differences in the effect of pyridoxine deficiency on the incorporation of radioactivity from dl-[3-¹⁴C]serine into DNA and RNA were observed, whereas the effect of the deficiency on the incorporation of radioactivity from [8-¹⁴C]adenine into spleen DNA was somewhat greater than that into spleen RNA. Administration of pyridoxine 24hr. before the rats were killed reversed the changes in incorporation of radioactivity from [3-¹⁴C]serine and [8-¹⁴C]adenine. 4. The adverse effects of pyridoxine deficiency on the biosynthesis of nucleic acids and cell multiplication are discussed in relation to the role of pyridoxal phosphate in the production of C₁ units via the serine-hydroxymethylase reaction.     

Evidence for a rapid effect of abscisic acid on amino acid metabolism in Lemna

Abscisic acid (ABA) causes an increase in free amino acid content of the fronds of Lemna minor, L. paucicostata and L. polyrrhiza within 6–12 h. This increase is followed by a temporary decline and a further, slower rise. Within 3 h of transfer to ABA, a substantial increase in medium amino nitrogen was detected indicating an increased rate of efflux, and possibly implying effects on membrane permeability.     

The effect of molybdenum on ascorbic acid metabolism in rats

1. The effect of dietary molybdenum on the growth rate and also on ascorbic acid metabolism in rats was studied. An excess of dietary molybdenum resulted in growth retardation and loss of weight. Tolerance to molybdenum was affected by the nature of the molybdenum salt administered. 2. Molybdenum ingestion altered certain aspects of ascorbic acid metabolism in rats. The conversion of d-glucuronolactone into l-ascorbic acid in vitro and the oxidative breakdown of l-ascorbic acid by liver enzymes decreased with high molybdenum intakes. The activity of liver uronolactonase was slightly inhibited. The activities of l-gulonate dehydrogenase and l-gulonate decarboxylase were not affected appreciably. 3. Molybdenum supplementation of the control diet resulted in an increase in ascorbic acid content of spleen and adrenal gland, and in a marked decrease in the urinary excretion of ascorbic acid and glucuronic acid. The implications of these findings are discussed.     

The effect of pyridoxine deficiency on the metabolism of the aromatic amino acids by isolated rat liver cells

The total activity of three key enzymes and the flux through eight steps of aromatic amino acid metabolism have been determined in liver cells isolated from rats fed either control or pyridoxine-free diet for 5-6 weeks. The pyridoxine-free diet caused a decrease in the catabolism of tyrosine and phenylalanine because of a drop in the flux through tyrosine aminotransferase. This decrease of expressed cellular tyrosine aminotransferase activity can be fully explained in terms of loss of cofactor. Larger decreases in the catabolism of tryptophan were seen after pyridoxine deprivation. The decreased extent of tryptophan catabolism can be solely attributed to loss of cofactor or increased degradation of kynureninase. Inhibition of tryptophan 2,3-dioxygenase was seen in pyridoxine deficiency, probably because of the buildup of the kynurenine metabolites. The control strength of kynureninase, for flux through kynureninase, was calculated to be less than or equal to 0.004, but 0.41 after pyridoxine deprivation. The sensitivity of the three pathways to pyridoxine deprivation is interpreted and discussed in terms of the different affinities for pyridoxal phosphate and the control strengths of the pyridoxal phosphate-dependent enzymes, tyrosine aminotransferase and kynureninase.     

Metabolomic analysis of amino acid and energy metabolism in rats supplemented with chlorogenic acid

This study was conducted to investigate effects of chlorogenic acid (CGA) supplementation on serum and hepatic metabolomes in rats. Rats received daily intragastric administration of either CGA (60 mg/kg body weight) or distilled water (control) for 4 weeks. Growth performance, serum biochemical profiles, and hepatic morphology were measured. Additionally, serum and liver tissue extracts were analyzed for metabolomes by high-resolution ¹H nuclear magnetic resonance-based metabolomics and multivariate statistics. CGA did not affect rat growth performance, serum biochemical profiles, or hepatic morphology. However, supplementation with CGA decreased serum concentrations of lactate, pyruvate, succinate, citrate, β-hydroxybutyrate and acetoacetate, while increasing serum concentrations of glycine and hepatic concentrations of glutathione. These results suggest that CGA supplementation results in perturbation of energy and amino acid metabolism in rats. We suggest that glycine and glutathione in serum may be useful biomarkers for biological properties of CGA on nitrogen metabolism in vivo.     

Metabolomic analysis of amino acid metabolism in colitic rats supplemented with lactosucrose

Intestinal inflammation causes metabolic disorders. The purpose of this study was to determine the effect of dietary supplementation with lactosucrose (LS) on the serum metabolome and intestinal luminal content of fatty acids in colitic rats. Colitis was induced in rats using trinitrobenzene sulfonic acid. Subsequently, rats received intragastric administration of either 250 mg LS/kg body weight or saline (the control group) every day for 5 weeks. Short-chain fatty acids in the intestinal lumen, blood profile, and metabolites in serum were measured, respectively, using gas chromatography, biochemistry analyzer, and nuclear magnetic resonance-based metabolomics combined with multivariate statistics. Metabolic effects of LS included: (1) decreases in concentrations of branched-chain amino acids (isoleucine and valine), alanine, citric acid, trimethylamine oxide and taurine, and the abundance of aspartate aminotransferase in serum; (2) increases in concentrations of glucose metabolites (including succinate) in serum; and (3) altered concentrations of butyrate in the cecal content and of butyrate and acetate in the colon content. The results indicate that LS supplementation to colitic rats affects whole-body metabolism of amino acids and release of aspartate aminotransferase and alkaline phosphatase from tissues into the blood circulation, and enhances the production of short-chain fatty acids in the intestinal lumen.